Recently, various types of electronic devices including a mouse are being presented on the market as a position information input apparatus. An example of the electronic devices is an information input apparatus using ultrasonic waves. The position information input apparatus using ultrasonic waves serves to input position information, by measuring a position of a pen-shaped signal generating device, based on distances between the signal generating device and ultrasonic signal receiving sensors, and a distance between the ultrasonic signal receiving sensors. In this case, the distances are obtained by using differences between a time when a reference signal (e.g., infrared ray, RF signal, etc.) has been received, and times when ultrasonic signals have been received by the ultrasonic signal receiving sensors spaced from each other by a predetermined distance, respectively. The ultrasonic signals which propagate at a speed of sound, and the reference signal which propagates at a speed of light are simultaneously generated from the signal generating device. An example of such position information input apparatus has been disclosed in Korean Patent Publication No. 0418423.
The conventional position information input apparatus using an ultrasonic wave signal is composed of a signal generator and an ultrasonic wave receiver. For a user's free input of position information, both of the signal generator and the ultrasonic wave receiver should be implemented as wireless devices.
However, all signal generators and ultrasonic wave receivers being currently presented out on the market, have commercial batteries (e.g., AA size or mercury cells, etc.) therein. If the battery is used up, a new battery is purchased for replacement. However, since a user cannot precisely predict the lifespan of the battery, an operation of the product may be stopped due to exhaustion of the battery.
Further, since the signal generator and the ultrasonic wave receiver are manufactured as separate products, a user should carry them separately. This may cause a user's inconvenience, resulting in lowering a utilization degree of the product.